Hydrostatic-drive tractor

Abstract

A narrow gauge, hydrostatic-drive tractor comprises an air-cooled prime mover, a Sundstrand hydraulic transmission mechanically coupled thereto, a fixed-displacement hydraulic motor hydraulically coupled to the Sundstrand transmission, an air conduit extending vertically upward from the fan housing of the prime mover for supplying ambient air to cool the prime mover, and cooling device disposed in the air conduit functioning to cool the hydraulic fluid. The motor is disposed beneath the fan housing and is coupled through a differential to drive wheels which, advantageously, have a diameter substantially the same as the width of the tractor. Advantageously, also, a manually-operated selector valve and a pressure-actuated cross-over relief valve is provided for by-passing the motor to protect the motor and to permit the tractor to be moved manually. There is also disclosed a scraping device for use with the above or like narrow gauge tractor.

I claim: 
     
       1. A narrow gauge, hydrostatic-drive tractor comprising an air-cooled prime mover having a rearwardly-projecting drive shaft, a variable-displacement, reversible hydraulic pump having a forwardly-projecting driven shaft coupled with the drive shaft of said prime mover by direct mechanical coupling, a fixed-displacement hydraulic motor having a forwardly-projecting drive shaft and being hydraulically-coupled to said pump by means of a hydraulic circuit in which the output of said pump is supplied directly to the input of said motor and the output of said motor is supplied directly to the input of said pump; a fan and fan housing at the forward end of said prime mover;   an air conduit means extending vertically-upward from said fan housing for supplying ambient air to cool said prime mover;   cooling means disposed in said air conduit means in heat-exchange with the ambient air drawn in, said cooling means functioning to cool the hydraulic fluid in said hydraulic circuit, and said motor being disposed directly beneath said fan housing with its drive shaft projecting beyond said housing;   differential means having transverse axles and a rearwardly-projecting driven shaft which driven shaft is disposed directly above the drive shaft of said motor and mechanically-coupled thereto; and drive wheels mounted on said axles.   
     
     
       2. A narrow gauge, hydrostatic-drive tractor according to claim 1, in which said tractor has a single guide wheel located beneath said hydraulic pump. 
     
     
       3. A narrow gauge, hydrostatic-drive tractor comprising an air-cooled prime mover having a drive shaft, a variable-displacement, reversible hydraulic pump having a driven shaft coupled with the drive shaft of said prime mover by direct mechanical coupling, a fixed-displacement hydraulic motor having a drive shaft and being hydraulically-coupled to said pump by means of a hydraulic circuit in which the output of said pump is supplied directly to the input of said motor and the output of said motor is supplied directly to the input of said pump; a fan and fan housing at the end of said prime mover opposite the drive shaft;   an air conduit means extending vertically-upward from said fan housing for supplying ambient air to cool said prime mover;   cooling means disposed in said air conduit means in heat-exchange with the ambient air drawn in, said cooling means functioning to cool the hydraulic fluid in said hydraulic circuit, and said motor being disposed beneath said fan housing with its drive shaft projecting beyond said housing; and,   differential means having transverse axles and a driven shaft, which driven shaft is disposed above the drive shaft of said motor and mechanically-coupled thereto, and drive wheels mounted on said axles; in which said prime mover, said pump, and said motor are supported by a frame comprising longitudinal, parallel beams, the front ends of which are supported in and form a unitary part of the housing of said differential and the rear ends of which are supported by a vertically-trunnioned, guide-wheel assembly adapted to rotate about its vertical trunnion to steer the tractor, and in which the diameter of said wheels is substantially the same as the spacing from the outside of one wheel to the outside of the other wheel.   
     
     
       4. The narrow qauge, hydrostatic-drive tractor of claim 3, in which said wheels are separated from each other by less than two widths of said wheels and in which said frame carries a superstructure which extends up over said wheels supporting an operator's seat. 
     
     
       5. The narrow gauge, hydrostatic-drive tractor of claim 4, in which said air conduit means is disposed between said wheels and between said seat and said prime mover. 
     
     
       6. The narrow gauge, hydrostatic-drive tractor of claim 4, in which the overall width of the tractor is not substantially greater than the diameter of said wheels. 
     
     
       7. The narrow gauge, hydrostatic-drive tractor of claim 4, which comprises a vertical steering column adjacent said seat and a roller-chain drive means connecting said steering column with said guide wheel. 
     
     
       8. The narrow gauge, hydrostatic-drive tractor of claim 7, in which said roller-chain drive means comprises two chains, the first of which connects the steering column with a sprocket at the bottom of a vertically-disposed trunnion, and the second of which connects said guide wheel to a sprocket at the top of said vertically-disposed trunnion, said sprockets and said vertically-disposed trunnion being unitary, whereby rotation of the bottom sprocket by said steering column causes rotation of the upper sprocket which, in turn, causes rotation of said guide wheel. 
     
     
       9. The narrow gauge, hydrostatic-drive tractor of claim 8, in which the first of said chains is disposed along the bottom of one side of said frame and extends from said bottom sprocket to and around a plurality of front end sprockets, one of which is unitary with said steering column. 
     
     
       10. The narrow gauge, hydrostatic-drive tractor of claim 9, in which said front end sprockets are mounted on the bottom of a transverse member affixed to the bottom of said forward portion of said superstructure. 
     
     
       11. The narrow gauge, hydrostatic-drive tractor of claim 10, in which said front end sprockets comprise two direct sprockets and two idler sprockets. 
     
     
       12. The narrow gauge, hydrostatic-drive tractor of claim 11, in which the sprocket which is unitary with said steering column is an idler sprocket. 
     
     
       13. The narrow gauge, hydrostatic-drive tractor of claim 11, in which said first chain comprises tightening means for tightening said chain about said sprockets. 
     
     
       14. The narrow gauge, hydrostatic-drive tractor of claim 13, in which said tightening means comprises a turnbuckle in said chain. 
     
     
       15. The narrow gauge, hydrostatic-drive tractor of claim 3, which comprises a transverse guide holder mounted rearward of said guide wheel. 
     
     
       16. The narrow gauge, hydrostatic-drive tractor of claim 15, in which said transverse tool holder is affixed to arms pivotally mounted on a transverse trunnion journaled in said frame forward of said guide wheel, whereby said guide holder can be raised or lowered. 
     
     
       17. The narrow gauge, hydrostatic-drive tractor of claim 16, which comprises means for raising and lowering said guide holder comprising a bell crank unitary with one of said arms, a control lever adjacent said seat, and a connecting rod connecting said bell crank and said lever in such a manner that forward motion of said control lever causes said guide holder to be raised. 
     
     
       18. A narrow gauge, hydrostatic-drive tractor comprising: a frame;   a single guide wheel at the rearward end of said frame;   a pair of drive wheels at the forward end thereof which are driven through a differential;   a prime mover in between, having a rearwardly-projecting drive shaft;   a hydrostatic-drive unit comprising a variable-displacement, reversible hydraulic pump having a forwardly-projecting driven shaft in line with said drive shaft and directly coupled thereto by a mechanical coupling; and,   a remote fixed-displacement hydraulic motor, hydraulically-coupled with said hydraulic pump and directly mechanically-connected to said differential; said hydraulic pump being disposed closely adjacent to said prime mover and said hydraulic motor being disposed beneath said prime mover with substantially only its drive shaft projecting forwardly beyond the same.   
     
     
       19. A narrow gauge, hydrostatic-drive tractor comprising a prime mover having a rearwardly-projecting drive shaft;   a variable-displacement, reversible hydraulic pump having a forwardly-projecting driven shaft in line with said drive shaft and directly coupled thereto by direct mechanical coupling;   a fixed-displacement hydraulic motor having a drive shaft and being hydraulically-coupled to said pump by means of a hydraulic circuit in which the output of said pump is supplied directly to the input of said motor and the output of said motor is supplied directly to the input of said pump, said motor being disposed beneath said prime mover with its drive shaft projecting forwardly beyond the same; and,   differential means having transverse axles having drive wheels mounted thereon and a rearwardly-projecting driven shaft which driven shaft is disposed above the forwardly-projecting drive shaft of said motor and mechanically-coupled thereto.   
     
     
       20. A narrow gauge tractor which comprises drive wheels mounted on a differential driven by a prime mover through a hydrostatic transmission comprising a variable-displacement, reversible hydraulic pump hydraulically-coupled to a hydraulic motor which, in turn, is mechanically-connected to said differential; said prime mover and said transmission being supported by a frame comprising longitudinal, parallel beams, the front ends of which are supported in and form a unitary part of the housing of said differential and the rear ends of which are supported by a vertically-trunnioned, guide-wheel assembly adapted to rotate about its vertical trunnion to steer the tractor, and in which the diameter of said drive wheels is substantially the same as the spacing from the outside of one wheel to the outside of the other wheel.